JP7555843B2 - Electrochromic element, lens unit having same, and imaging device - Google Patents

Description

The present invention relates to an electrochromic element, a lens unit having the electrochromic element, and an imaging device.

An electrochromic (hereinafter sometimes referred to as "EC") element is an optical element having a pair of electrodes and an EC layer disposed between the electrodes, which adjusts the hue and light quantity in the visible light band by applying a voltage between the pair of electrodes to oxidize or reduce a compound in the EC layer.
EC elements have been applied to products such as variable transmittance windows in aircraft and anti-glare mirrors in automobiles, and in recent years, attempts have been made to apply them to apertures and shutters for imaging devices, as well as ND filters, half ND filters, apodization filters, etc. Apodization filters are optical elements that smooth the contours of blurred images, and have a transmittance distribution in which the transmittance decreases with increasing distance from the optical axis.
Patent Document 1 discloses a technology in which a conductive connecting part that shorts a pair of electrodes is provided at the center of an EC element, and a voltage is applied from the outer periphery of the element, thereby increasing the voltage drop from the outer periphery to the center of the element, thereby achieving a desired transmittance distribution.

Special Publication No. 2002-537582

In the above-mentioned conventional EC element, a preferable transmittance distribution is realized by defining the resistance range of the electrodes, but the configuration requirements are not sufficiently set. That is, the transmittance distribution of a solution-type EC element depends on the resistance ratio of the electrode resistance to the solution resistance per unit width, and the resistance ratio specifically depends on the sheet resistance of the electrodes, the diameter of the dimming region, the distance between the pair of electrodes, and the resistivity of the electrochromic layer (solution). Therefore, in order to realize a preferable transmittance distribution, it was necessary to define these.
An object of the present invention is to provide a solution-based EC element that supplies power from the outer periphery of a light control region, and further, an EC element that can form a suitable transmittance distribution by making it follow the aperture diameter of a mechanical diaphragm of a lens. Also, an object of the present invention is to provide a lens unit and an imaging device with excellent optical characteristics by using such an EC element.

The first aspect of the present invention is an electrochromic element having a pair of electrodes and an electrochromic layer disposed between the pair of electrodes, the electrochromic element having a circular shape in a dimming region as viewed from a normal direction of the electrodes,
When the sheet resistance of the electrode is _rs [Ω], the resistance is r [Ω], the diameter of the dimming area is L [m], the distance between the pair of electrodes is d [m], the resistivity of the electrochromic layer is ρ [Ωm], and the resistance is R [Ω], the resistance ratio (r/R) of the electrode to the electrochromic layer, as shown in the following formula (1), is 2 or more and 20 or less.
r/R=( _rs L ² )/(ρd) (1)
A second aspect of the present invention is a lens unit having an imaging optical system having a plurality of lenses and a photochromic element that electrically controls an apodization effect on the imaging optical system,
The light control element is characterized in that it is the electrochromic element of the present invention.
A third aspect of the present invention is an imaging device having an imaging optical system having a plurality of lenses, a light control element that electrically controls an apodization effect on the imaging optical system, and an imaging element that receives light that has passed through the imaging optical system,
The light control element is characterized in that it is the electrochromic element of the present invention.

According to the present invention, a suitable transmittance distribution is realized by specifying the resistance ratio between the electrodes and the electrochromic layer, which is determined from the sheet resistance of the electrodes, the diameter of the dimming area, the electrode spacing, and the resistivity of the electrochromic layer. Furthermore, a suitable transmittance distribution is realized by making it follow the aperture diameter of the mechanical diaphragm of the lens. Therefore, the electrochromic element of the present invention is preferably used as a variable apodization filter. Furthermore, by using the optical element of the present invention, a lens unit and an imaging device having an excellent apodization effect are provided.

1A and 1B are schematic end views showing a planar shape and a schematic end view in a thickness direction of an embodiment of an EC element of the present invention. FIG. 13 is a diagram showing the transmittance distribution of an EC element in which the resistance ratio is changed only by the sheet resistance of the electrodes. FIG. 13 is a diagram showing the transmittance distribution when the voltage is increased for an EC element having a resistance ratio of 9.8. 13 is a diagram showing the transmittance distribution of an EC element when the effective diameter ratio position at which the normalized transmittance is 0.045 is normalized as effective aperture=1. 1 is a graph showing normalized transmittance at a position where the effective aperture is 0.7 with respect to voltage. FIG. 13 shows the transmittance distribution of EC devices with different electrode sheet resistances and dimming region diameters but the same resistance ratio. FIG. 2 is a schematic end view showing a power supply position to a bus line of the EC element according to the first embodiment of the present invention. FIG. 11 is a schematic end view showing a power supply position to a bus line of an EC element according to a fourth embodiment of the present invention. 1 is a diagram illustrating a schematic configuration of an embodiment of an imaging device having a lens unit of the present invention.

Below, a preferred embodiment of the configuration of the electrochromic element (EC element) according to the present invention will be described in detail with reference to the drawings. However, the configuration, relative arrangement, etc. described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified.

[EC element]
First, the configuration of the EC element of the present invention will be described with reference to Fig. 1. Fig. 1(a) is a diagram showing the planar shape of an EC element 6 according to one embodiment of the present invention, and Fig. 1(b) is a diagram showing the cross-sectional shape. Fig. 1(a) is a schematic diagram of an end surface of the EC element 6 taken at the position B-B' in Fig. 1(b), and Fig. 1(b) is a schematic diagram of an end surface of the EC element 6 taken at the position A-A' passing through the center of the element in Fig. 1(a).

As shown in FIG. 1, the EC element 6 is composed of a pair of substrates 1a, 1b on which a pair of electrodes 2a, 2b are formed, and an electrochromic layer (EC layer) 5 arranged in a space defined by the pair of electrodes 2a, 2b and a sealant 4. Outside the sealant 4, on the outer periphery of each of the pair of transparent electrodes 2a, 2b, bus wiring 3a, 3b is formed in an annular shape to ensure uniform voltage application from outside the element. In FIG. 1(a), the area surrounded by the sealant 4 is the dimming area of the EC element 6, and when viewed from the normal direction of the electrodes 2a, 2b, the shape of the dimming area is circular. The components that make up the EC element 6 will be described in detail.

(EC layer)
The EC layer 5 is preferably a solution layer in which an electrochromic compound (EC compound) is dissolved in an organic solvent, and the solution layer may contain an electrolyte. The EC layer 5 can be formed by injecting a liquid containing an EC compound, which has been prepared in advance, into the gap between the electrodes 2a and 2b by a vacuum injection method, an air injection method, a meniscus method, or the like.

The EC compounds used in the present invention are anodic electrochromic compounds that change color from a transparent state by an oxidation reaction, or cathodic electrochromic compounds that change color from a transparent state by a reduction reaction, and both may be used. In addition, the EC compounds are preferably organic compounds. The use of both an anodic EC compound and a cathodic EC compound is preferable because it increases the coloring efficiency with respect to the current. In this specification, an element having both an anodic EC compound and a cathodic EC compound is called a complementary EC element. The anodic EC compound is also called an anode material, and the cathodic EC compound is also called a cathode material. In addition, in the present invention, an anodic compound or a cathodic compound that does not change color even when an oxidation reaction or a reduction reaction occurs, i.e., that is not an EC compound, may be used in addition to the above EC compounds.

When a complementary EC element is driven, an oxidation reaction at one electrode extracts electrons from the EC compound, and a reduction reaction at the other electrode receives electrons from the EC compound. Radical cations may be generated from neutral molecules by the oxidation reaction. Radical anions may be generated from neutral molecules by the reduction reaction, or radical cations may be generated from dicationic molecules. Since the EC compound is colored at both electrodes 2a and 2b on the substrates 1a and 1b, it is preferable to use a complementary EC element when a large change in optical density is required during coloring.

Organic EC compounds include conductive polymers such as polythiophene and polyaniline, viologen compounds, anthraquinone compounds, oligothiophene derivatives, phenazine derivatives, and other organic low molecular weight compounds.

The EC layer 5 may have only one type of EC compound, or may have multiple types of EC compounds. When the EC layer 5 contains multiple types of EC compounds, it is preferable that the difference in redox potential of the EC compounds is small. When the EC layer 5 contains multiple types of EC compounds, the EC compounds may have four or more types of EC compounds, including the anodic EC compounds and the cathodic EC compounds, or five or more types of EC compounds. When the EC layer 5 contains multiple types of EC compounds, the redox potential of the multiple anode materials may be within 60 mV, and the redox potential of the multiple cathode materials may be within 60 mV. When the EC layer 5 contains multiple types of EC compounds, the multiple types of EC compounds may include a compound having an absorption peak from 400 nm to 500 nm, a compound having an absorption peak from 500 nm to 650 nm, and a compound having an absorption peak at 650 nm or more. The absorption peak refers to a peak with a half-width of 20 nm or more. In addition, the state of the material when absorbing light may be an oxidized state, a reduced state, or a neutral state.

The electrolyte that may be contained in the EC layer 5 is not limited as long as it is an ion-dissociating salt and has good solubility in a solvent and high compatibility with a solid electrolyte. Among them, an electrolyte having electron donating properties is preferable. These electrolytes can also be called supporting electrolytes. Examples of the electrolyte include inorganic ion salts such as various alkali metal salts and alkaline earth metal salts, quaternary ammonium salts, and cyclic quaternary ammonium salts. Specific examples of the compounds include alkali metal salts of Li, _Na , and K, such as _LiClO4 , LiSCN, _LiBF4 , _LiAsF6 , _LiCF3SO3 , _LiPF6 , LiI, NaI, NaSCN, _{NaClO4 , NaBF4} , _NaAsF6 , KSCN, _and KCl, ( _CH3 ) _4NBF4 , ( _C2H5 ) _4NBF4 , (n- _C4H9 ) _{4NBF4 , (} n- _C4H9 ) _{4NPF6 ,} ( _C2H5 ) _4NBr , ( _C2H5 ) _{4NClO4 , and} (n _{- C4H9} ) _{4NClO .} ammonium salts such as quaternary ammonium salts of ₄ and cyclic quaternary ammonium salts.

The solvent for dissolving the EC compound and the electrolyte is not particularly limited as long as it can dissolve the EC compound and the electrolyte, but it is preferable to use a solvent that has polarity. Specific examples include water and organic polar solvents such as methanol, ethanol, propylene carbonate, ethylene carbonate, dimethyl sulfoxide, dimethoxyethane, γ-butyrolactone, γ-valerolactone, sulfolane, dimethylformamide, dimethoxyethane, tetrahydrofuran, acetonitrile, propionitrile, 3-methoxypropionitrile, benzonitrile, dimethylacetamide, methylpyrrolidinone, and dioxolane.

The EC layer 5 may further contain a polymer matrix or a gelling agent. In this case, the EC layer 5 becomes a highly viscous liquid, and in some cases becomes gel-like. Examples of polymers include polyacrylonitrile, carboxymethylcellulose, pullulan-based polymers, polyvinyl chloride, polyethylene oxide, polypropylene oxide, polyurethane, polyacrylate, polymethacrylate, polyamide, polyacrylamide, polyester, Nafion (registered trademark), etc., and PMMA is preferably used.

(substrate)
The pair of substrates 1a, 1b are both transparent and made of glass materials such as colorless or colored glass, reinforced glass, etc. As these glass materials, optical glass substrates such as #7059 and BK-7 manufactured by Corning Incorporated can be suitably used. Furthermore, the substrates 1a, 1b are preferably made of a material that is highly rigid and unlikely to cause distortion. In the present invention, "transparent" refers to a state in which the visible light transmittance is 50% or more.

(electrode)
Both of the electrodes 2a and 2b are transparent, and examples of the materials that can be used include indium tin oxide (ITO), fluorine-doped tin oxide (FTO), tin oxide (NESA), indium zinc oxide (IZO), graphene, etc. In addition, conductive polymers whose conductivity has been improved by doping treatment or the like, such as polyaniline, polypyrrole, polythiophene, polyacetylene, polyparaphenylene, and a complex of polyethylenedioxythiophene (PEDOT) and polystyrenesulfonic acid, can also be suitably used.

The EC element 6 according to the present invention preferably has high transmittance in the decolorized state, so the electrodes 2a and 2b are particularly preferably made of transparent materials such as ITO, IZO, NESA, PEDOT:PSS, graphene, etc. These can be used in various forms such as bulk and fine particles. These electrodes may be used alone or in combination.

(bus wiring)
The bus wirings 3a and 3b are formed as power supply parts for compensating for uniform voltage application from outside the dimming region, and a low-resistance metal material can be suitably used. For example, thin films of silver, palladium, copper, aluminum, silver-palladium-copper alloy (APC), aluminum-neodymium alloy, etc. can be suitably used. The bus wirings 3a and 3b are preferably formed in a ring shape surrounding the dimming region on the outer periphery of the electrodes 2a and 2b, and in order to prevent a voltage drop in the bus wirings 3a and 3b, it is preferable to provide multiple power supply parts for each bus wiring. For example, it is preferable to provide four power supply parts symmetrically for each bus wiring, and to rotate only one of the substrates 45° from the arrangement where the power supply parts overlap and then bond them together, thereby making the bus wiring arrangement and power supply part arrangement as symmetrical as possible with respect to the center of the element.

(Sealing material)
The sealing material 4 is preferably a material that is chemically stable, impermeable to gases and liquids, and does not inhibit the oxidation-reduction reaction of the EC compound. Examples of the material include inorganic materials such as glass frit and organic materials such as epoxy resin.
The EC element 6 of the present invention may have a spacer that defines the distance between the electrodes 2 a and 2 b. The function of the spacer may be performed by the sealing material 4. The spacer may be made of an inorganic material such as silica beads or glass fiber, or an organic material such as polydivinylbenzene, polyimide, polytetrafluoroethylene, fluororubber, or epoxy resin.

[Resistance ratio between electrode and EC layer]
Next, the ratio (r/R) of the electrode resistance r to the resistance R of the EC layer, which is a feature of the present invention, will be described. First, the electrode resistance r [Ω] per unit width Δw [m] in the diameter L [m] of the light control area (see FIG. 1B) is expressed as follows, using the sheet resistance r _s [Ω]:
r = (L/Δw) _r
It can be expressed as:

Furthermore, the resistance R [Ω] of the EC layer in the thickness direction per unit width Δw [m] in the diameter L [m] of the light control region is calculated using the resistivity ρ [Ωm] of the EC layer and the distance d [m] between the pair of electrodes (see FIG. 1B ).
R=(d/(ΔwL))ρ
Therefore, the resistance ratio (r/R) is expressed as follows: r/R=(r _s L ² )/(ρd) (1)
and is expressed using four independent parameters.

Here, we will explain the resistivity ρ of the EC layer. The resistance of the EC layer is expressed as the sum of three resistance components: the solution resistance that does not involve an electrochemical reaction, the charge transfer resistance associated with the charge transfer reaction between the EC compound molecules and the electrodes, and the diffusion resistance associated with the diffusion of the EC compound molecules in the EC layer. These three resistance components vary greatly depending on the concentration of the EC material and additives such as the solvent and thickener, but can be easily determined by performing an AC impedance analysis of the EC element.

2 shows the transmittance distribution when the resistance ratio (r/R) is changed between 1.6 and 22.9 by changing only the sheet resistance r _s of the electrode among the four parameters of formula (1). Here, the transmittance (T) is the normalized transmittance (T/T 0 ) normalized by setting the transmittance (T ₀ ) of the center value of the EC element to 1, and the condition is given that the normalized transmittance (T/T ₀ ) = 0.045 (corresponding to 4.5 steps of dimming from the center of the element) at the position of the effective diameter ratio Φ = 1.0. The four parameters and resistance ratio values set at _this time are shown in Table 1.

It can be seen that as the resistance ratio (r/R) becomes smaller, the transmittance at the intermediate effective diameter ratio position decreases. When an image simulation was performed using the transmittance distribution obtained in this way, it was found that as the resistance ratio becomes smaller, the contour becomes more blurred, but the blurred image becomes smaller.

At a resistance ratio (r/R) of 22.9 (sheet resistance r _s =140Ω), the size of the blurred image is sufficient, but the gradation effect is small, and it is not preferable as an apodization filter. At a resistance ratio (r/R) of 1.6 (sheet resistance r _s =10Ω), the gradation effect of the blurred image is large, but the image becomes too small, and it is not preferable as an apodization filter. Therefore, it can be said that the range of the resistance ratio (r/R) that can realize a suitable transmittance distribution as an apodization filter is 2 or more and 20 or less. Furthermore, when this is converted into a suitable range of the normalized transmittance (T/T ₀ ) at the position of the effective diameter ratio Φ=0.7, it is 0.3 or more and 0.75 or less, preferably 0.5 or more and 0.75 or less. Here, the position of the effective diameter ratio Φ=0.7 is the position where the change in the normalized transmittance (T/T ₀ ) when the resistance ratio (r/R) is changed is close to the maximum.

[Adapting to changes in caliber]
Next, with regard to an EC element having a suitable resistance ratio range (an element having (r/R)=9.8 in Table 1), it will be explained that even when the voltage applied is increased to make it follow the mechanical aperture, the transmittance distribution can be kept within a suitable range by normalizing it with the effective aperture of the EC element.

Figure 3 shows the transmittance distribution when the applied voltage is increased for an EC element with a resistance ratio of 9.8 (sheet resistance r _s = 60Ω). It can be seen that the effective aperture gradually narrows as the voltage is increased. Therefore, the transmittance distribution normalized for each voltage plot, with the effective aperture ratio Φ _0.045 at which the normalized transmittance (T/T ₀ ) = _0.045 is set to 1, is shown in Figure 4. It can be seen that the transmittance at the intermediate position gradually decreases as the voltage is increased.

FIG. 5 shows a plot of normalized transmittance (T/T ₀ ) at the effective aperture (Φ/Φ _0.045 )=0.7 versus voltage. The dashed lines above and below the plot indicate the lower limit of 0.3 and the upper limit of 0.75 of the suitable range of normalized transmittance (T/T ₀ ), which corresponds to the suitable range of resistance ratio (r/R) of 2 to 20. Table 2 also shows the parameter settings at each voltage and the normalized transmittance (T/T ₀ ) at the effective aperture (Φ/Φ _0.045 )=0.7. It can be seen that the normalized transmittance (T/T ₀ ) decreases approximately linearly with the voltage, but is within the suitable range of normalized transmittance (T/T ₀ ), which is 0.3 to 0.75.

By increasing the voltage from 0.7 V to 1.4 V, the effective aperture becomes smaller to an effective diameter ratio Φ of about 0.7 (corresponding to a change in aperture diameter of one stop) as shown in FIG. 3. However, even in this case, the transmittance distribution is still within the preferable range when viewed from the effective aperture (Φ/Φ _0.045 ).
The decrease in transmittance at the intermediate position corresponding to this one-stage aperture change is 0.18, and since the width of the preferred transmittance range is 0.45, if the resistance ratio (r/R) is set near the upper limit of the range, it is possible to follow an aperture change of two or more stages. Therefore, a more preferred range for the resistance ratio (r/R) that can realize a preferred transmittance distribution as a variable apodization filter is 9 to 20.

[Parameter settings]
Next, with regard to an EC element having a suitable resistance ratio (r/R), it will be explained that even if the sheet resistance r _s of the electrode and the diameter L of the dimming region are changed simultaneously, the same transmittance distribution will be formed as long as the resistance ratio (r/R) remains the same.
Table 3 shows the four set parameters, the resistance ratio (r/R), and the normalized transmittance (T/T ₀ ) at the position where the effective diameter ratio Φ=0.7.

6 shows the transmittance distributions of the three EC elements in Table 3 that have the same resistance ratio (r/R) of 9.8, but different electrode sheet resistances _rs and dimming region diameters L. It can be seen that the same transmittance distribution is formed when the resistance ratio (r/R) is the same, regardless of the electrode resistance r or dimming region diameter L.

[Uses of EC elements]
The EC element of the present invention is used as a light control element that electrically controls the apodization effect. Specifically, it can be applied as a variable apodization filter to a lens unit and an image pickup device.

(Lens unit and imaging device)
9 shows an imaging device 10 having a lens unit 11 to which the EC element 6 of the present invention is applied. The lens unit 11 is detachably connected to an imaging unit 12 via a mount member. The EC element 6 of the present invention is often incorporated into the lens unit 11, particularly into the imaging optical system 20. In that sense, when the lens unit 11 and the imaging unit 12 are detachable, it is called a lens unit, and when they are not detachable, it is called an imaging device.

The imaging optical system 20 in the lens unit 11 is composed of multiple lens groups. In this specification, a lens group is a group of lenses that move or stand still as a unit during focusing, and the distance between adjacent lens groups changes during focusing from infinity to a close distance. Note that a lens group may be composed of a single lens or multiple lenses.

The imaging optical system 20 has a mechanical aperture 13 and an EC element 6, which operate in response to an input signal from a control unit (not shown). The imaging optical system 20 has a three-group configuration consisting of a first lens group 21 having a positive refractive index, a second lens group 22 having a negative refractive index, and a third lens group 23 having a positive refractive index. The ninth surface is the mechanical aperture 13, and the tenth and eleventh surfaces are the entrance and exit surfaces of the EC element 6, respectively, that is, adjacent to the image side of the mechanical aperture 13. In the imaging device 10, focusing is performed by moving the second lens group 22 having a negative refractive index toward the image side. In FIG. 9, the EC element 6 is an example in which one EC element is arranged adjacent to the mechanical aperture 13, but multiple EC elements 6 can be arranged in any optimal position depending on the lens configuration.

Light that passes through the lens unit 11 reaches the imaging unit 12, passes through a glass block such as a low-pass filter, face plate, or color filter (not shown), and is received by the imaging element 14. The imaging element 14 can be a CCD or CMOS. It can also be an optical sensor such as a photodiode, and it is possible to use one that acquires and outputs information on the intensity or wavelength of light.

When the EC element 6 of the present invention is incorporated in the lens unit 11 as shown in FIG. 9, the driving means for the element may be disposed within the lens unit 11, or may be disposed outside the lens unit 11, such as in the imaging unit 12. When disposed outside the lens unit 11, the EC element and the driving means in the lens unit 11 are connected via wiring to perform driving control.

Such lens units can be applied to various imaging devices, such as cameras, digital cameras, video cameras, digital video cameras, etc., and can also be applied to products that incorporate imaging devices, such as mobile phones, smartphones, PCs, and tablets.

Example 1
An EC element having the configuration shown in FIG. 1 and a circular dimming region with a diameter L of 46 mm was fabricated. This is an example in which the sheet resistance r _s of the pair of transparent electrodes 2a and 2b is 60Ω, the electrode spacing d is 30 μm, and the resistivity ρ of the EC layer 5 is 430.88Ωm, and therefore the resistance ratio (r/R) calculated from formula (1) is 9.8. A thermosetting epoxy resin is used as the seal material 4 for bonding the pair of transparent electrode substrates, and gap control particles with a diameter of 30 μm are kneaded into this to define the electrode spacing. The width of the seal material 4 after bonding was about 1.0 mm.

On the electrodes 2a and 2b outside the sealing material 4, a circular dimming region and a pair of bus wires 3a and 3b were arranged in a manner surrounding the sealing material 4. The bus wires 3a and 3b were formed by sputtering a silver thin film (sheet resistance = 14 mΩ) with a thickness of 1.2 μm and a width of 2.0 mm. There were three power supply points on each pair of bus wires 3a and 3b, and the bus wires 3a and 3b were arranged alternately at 60° intervals. Figure 7 shows the power supply positions of the EC element of this embodiment. Figure 7 is a schematic end view of the same position as Figure 1(a), in which 7b is the power supply position to the bus wire 3b formed on the electrode 2b, and 7a is the power supply position to the bus wire 3a (not shown) formed on the electrode 2a (not shown).

When a constant voltage of 0.7 V to 1.4 V was applied to the EC element having the above configuration, the normalized transmittance distribution was as shown in Figure 3. At this time, the normalized transmittance distribution converted based on the effective aperture (effective aperture ratio Φ _0.045 ) was as shown in Figure 4, and the transmittance distribution was within the desirable range.
At this time, the effective aperture was reduced to about 70%, and it was possible to operate the device while maintaining a suitable transmittance distribution by following a change in aperture of about one step of the mechanical diaphragm.

Example 2
An EC element was fabricated having the same configuration as in Example 1, except that the sheet resistance r _s of the transparent electrodes 2a and 2b was set to 20 Ω and the resistance ratio (r/R) was set to 3.3.
When a constant voltage of 0.7 V was applied to the EC element of this example, it exhibited a normalized transmittance distribution as shown by the curve "r/R=3.3" in FIG.

Example 3
An EC element was fabricated having the same configuration as in Example 1, except that the sheet resistance r _s of the transparent electrodes 2a and 2b was set to 120Ω, and the resistance ratio (r/R) was 19.6.
When a constant voltage of 0.7 V to 2.0 V was applied to the EC element of this example, the effective aperture was reduced to an effective aperture ratio of about Φ = 0.5, and the normalized transmittance distribution converted to the effective aperture (effective aperture ratio Φ _0.045 ) was able to fall within the range of the suitable transmittance distribution. In other words, it was possible to operate the element while maintaining a suitable transmittance distribution by following a change in aperture of about two stops of the mechanical diaphragm.

Example 4
An EC element having the same configuration as that of Example 1 was fabricated, except that the diameter L of the dimming region was set to 72 mm, the sheet resistance r _s of the transparent electrodes 2a and 2b was set to 24.5Ω, the resistance ratio (r/R) was set to 9.8, and the bus wirings 3a and 3b and the power supply positions to the bus wirings 3a and 3b were changed. The bus wirings 3a and 3b were formed by a sputtering method using a silver thin film (sheet resistance = 11 mΩ) having a film thickness of 1.5 μm and a width of 2.0 mm. In addition, as shown in FIG. 8, the power supply positions 7a and 7b to the bus wirings 3a and 3b were set to four positions each, and the bus wirings 3a and 3b were alternately arranged at 45° intervals. Note that FIG. 8 is a schematic end view of the same position as FIG. 1(a).

When a constant voltage of 0.7 V was applied to the EC element of this example, the transmittance distribution was approximately the same as that of Example 1 (r _s =60 Ω, L=46 mm), as shown by the curve "r _s =24.5 Ω, L=72 mm" in Figure 6. When the voltage was further increased to apply a constant voltage of up to 1.4 V, the effective aperture was reduced to an effective aperture ratio of about Φ=0.7, and the normalized transmittance distribution converted by the effective aperture (effective aperture ratio Φ _0.045 ) was able to fall within the range of the suitable transmittance distribution. In other words, it was possible to operate the element while maintaining a suitable transmittance distribution by following the change in aperture of about one step of the mechanical aperture.

Example 5
An EC element was fabricated having the same configuration as in Example 1, except that the diameter L of the light control region was 30 mm, the sheet resistance _rs of the transparent electrodes 2a and 2b was 141Ω, and the resistance ratio (r/R) was 9.8.
When a constant voltage of 0.75 V was applied to the EC element of this example, the transmittance distribution was approximately the same as that of Example 1 (r _s =60 Ω, L=46 mm), as shown by the curve "r _s =141 Ω, L=30 mm" in Figure 6. When the voltage was further increased to apply a constant voltage of up to 1.5 V, the effective aperture was reduced to an effective aperture ratio of about 0.7, and the normalized transmittance distribution converted by the effective aperture (effective aperture ratio Φ _0.045 ) was able to fall within the range of the suitable transmittance distribution. In other words, it was possible to operate the element while maintaining a suitable transmittance distribution by following the change in aperture of about one step of the mechanical aperture.

2a, 2b: electrodes, 5: electrochromic layer, 6: electrochromic element, 10: imaging device, 11: lens unit, 14: imaging element, 20: imaging optical system

Claims (8)

An electrochromic element having a pair of electrodes and an electrochromic layer disposed between the pair of electrodes, the electrochromic element having a circular shape in a dimming region as viewed from a normal direction of the electrodes,
An electrochromic element characterized in that, when the sheet resistance of the electrode is _rs [Ω], the resistance is r [Ω], the diameter of the dimming area is L [m], the distance between the pair of electrodes is d [m], the resistivity of the electrochromic layer is ρ [Ωm], and the resistance is R [Ω], the resistance ratio (r/R) of the electrode to the electrochromic layer, as shown in the following formula (1), is 2 or more and 20 or less.
r/R=( _rs L ² )/(ρd) (1) The electrochromic element according to claim 1, characterized in that the resistance ratio (r/R) is 9 or more and 20 or less. The electrochromic element according to claim 1 or 2, characterized in that the normalized transmittance at a position where the effective diameter ratio is 0.7 is 0.3 or more and 0.75 or less. The electrochromic element according to claim 1 or 2, characterized in that the normalized transmittance at a position where the effective diameter ratio is 0.7 is 0.5 or more and 0.75 or less. An electrochromic element according to any one of claims 1 to 4, characterized in that a voltage is supplied to each of the pair of electrodes from the outer periphery. The electrochromic element according to any one of claims 1 to 5, characterized in that the electrochromic layer contains an anodic electrochromic compound and a cathodic electrochromic compound. A lens unit having an imaging optical system having a plurality of lenses and a light control element that electrically controls an apodization effect on the imaging optical system,
The light control element is an electrochromic element according to claim 1 . An imaging device having an imaging optical system having a plurality of lenses, a light control element that electrically controls an apodization effect on the imaging optical system, and an imaging element that receives light that has passed through the imaging optical system,
An imaging device, wherein the light control element is an electrochromic element according to claim 1 .

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